Sulphur cement generally refers to a product comprising at least sulphur and a filler. To improve the properties of the sulphur cement, the sulphur may be modified using a sulphur modifier, e.g. naphthalene or olefinic compounds such as 5 ethylidene-2-norbornene (ENB) or 5 vinyl-2-norbornene (VNB), dicyclopentadiene, limonene or styrene. Typical sulphur cement fillers are particulate inorganic materials.
Sulphur cement-aggregate composites generally refer to a composite comprising both sulphur cement and aggregate. Examples of sulphur cement-aggregate composites are sulphur mortar, sulphur concrete and sulphur-extended asphalt.
It is known to use organosilane compounds as a stabilising agent in sulphur cement or sulphur cement-aggregate compositions to improve water stability. In WO 2007/65920, sulphur cement or a sulphur cement-aggregate composite is prepared by admixing an inorganic filler and a polysulphide-containing organosilane, mixing with molten sulphur and solidifying the admixture.
It is desirable to incorporate the organosilane into the sulphur prior to its use in the sulphur cement manufacturing plant, thereby avoiding the need for additional and potentially complex process steps at the manufacturing plant. Organosilanes are typically liquid reagents and it is preferable to use solid reagents in the manufacturing plant. WO 2008/148804 discloses a process wherein the organosilane is incorporated into a sulphur cement pre-composition. The sulphur cement pre-composition can be mixed with particulate inorganic material and optionally with additional sulphur to provide a sulphur cement product.
The present inventors have however found that the sulphur pre-composition of WO 2008/148804 may be liable to degradation if stored for an extended period, particularly if the weight percentage of organosilane is high. Additionally, the organosilanes and molten sulphur can exhibit poor miscibility, which may lead to phase separations when preparing sulphur cement products. The present inventors have therefore sought to provide a method for preparing sulphur cement products which does not suffer from the disadvantages of the prior art, in particular a pre-composition that may be stored and does not phase separate when preparing sulphur cement products.